The company that's building the Whistle Bend extended care facility in Whitehorse says the building's shifting foundation is a "fairly minor issue," and won't affect the timing or budget for the project.

PCL Construction says frost is to blame for the shifting foundation on part of the project. The company halted work on that part of the building just about two weeks ago.

PCL district manager Todd Craigen says work stopped when the ground shifted under two different areas. He said ground frost underneath the concrete caused it to heave about 25 mm.

"From time to time, frost penetration does happen," Craigen said. "We obviously don't want it to happen, and protect against that, but unfortunately sometimes the weather gets past us. And it has happened in the past."

Craigen said the concrete was correctly applied in winter conditions.

"The concrete is always inspected, tested, and heated and hoarded to the design specifications," he explained.

"I don't know exactly right now, because our investigation is ongoing — perhaps the ground cover that we had, or the heating and hoarding wasn't broad enough to stop the frost penetration from getting below the concrete foundations."

Craigen says company engineers examined the site last week, and expect work can continue once the ground warms up.

He said the way to correct the problem is to thaw the ground "and let the frost retract.

"If it's an area that's accessible, we can apply heat to it to help the frost retract. But otherwise, just exposing it to above zero air temperatures will help the frost naturally retract from those areas.

"What we believe, and based on our preliminary assessment, [is that] as the frost retracts, the subsurface ground will assume its original profile," in other words, sink back down.

Craigen wondered why the issue was attracting media attention.

"I would characterize it as a fairly minor issue, a small issue that has maybe garnered more attention than it normally would have, on any other project."

'Frost will never touch those areas again'

Craigen says the heaving won't re-occur because the foundation will ultimately be backfilled, insulated and covered.

"Once the area is backfilled and the rest of the construction proceeds, frost will never touch those areas again."